Asano Y, Singer A, Hodes R J
J Immunol. 1985 Jun;134(6):3682-5.
It has previously been demonstrated that B cells can be activated through two distinct T helper (Th) cell-dependent pathways, one requiring both carrier-hapten linkage and MHC-restricted T-B interaction and the other requiring neither. In addition, it has been shown that different B cell subpopulations exist and that these subpopulations differ in their activation requirements. Previous studies demonstrated that resting B cells containing an Lyb-5+ subpopulation were activated by MHC-unrestricted T cell signals, whereas resting Lyb-5- B cells were activated only through MHC-restricted T-B interaction. It was suggested that this difference resulted from the ability of Lyb-5+ but not Lyb-5-B cells to respond to soluble MHC-unrestricted Th signals. Because Lyb-5+ B cells were responsive in these previous experiments to MHC-unrestricted Th signals, it could not be determined whether Lyb-5+ B cells were also responsive to MHC-restricted Th signals. Consequently, the present study was undertaken to directly address the question of whether Lyb-5+ B cells can be activated under appropriate conditions by MHC-restricted as well as unrestricted T cell-B cell interactions. It was found that unprimed normal B cells (containing Lyb-5+ and Lyb-5-B cells) but not unprimed xid-defective populations (Lyb-5- only) can be activated by cloned KLH-specific and MHC-restricted Th cells in response to either high or low concentrations of TNP-KLH. The IgM response of Lyb-5+-containing B cells to a high concentration of antigen (10 micrograms/ml) was MHC unrestricted, whereas the IgM response of unprimed Lyb-5+ B cells to a low concentration of antigen (0.001 micrograms/ml) was MHC restricted. Thus, unprimed Lyb-5+ B cells can be activated through both MHC-restricted and unrestricted pathways. It was further demonstrated that the activation requirements of Lyb-5+ and Lyb-5- B cells differed even for MHC-restricted B cell activation.
先前已经证明，B细胞可通过两条不同的T辅助（Th）细胞依赖性途径被激活，一条途径既需要载体 - 半抗原连接，也需要MHC限制的T - B相互作用，另一条途径则两者均不需要。此外，已经表明存在不同的B细胞亚群，并且这些亚群在激活要求上有所不同。先前的研究表明，含有Lyb - 5 +亚群的静息B细胞可被MHC非限制的T细胞信号激活，而静息的Lyb - 5 - B细胞仅通过MHC限制的T - B相互作用被激活。有人提出，这种差异是由于Lyb - 5 +而非Lyb - 5 - B细胞具有对可溶性MHC非限制的Th信号作出反应的能力。因为在这些先前的实验中Lyb - 5 + B细胞对MHC非限制的Th信号有反应，所以无法确定Lyb - 5 + B细胞是否也对MHC限制的Th信号有反应。因此，进行本研究以直接解决Lyb - 5 + B细胞在适当条件下是否可通过MHC限制以及非限制的T细胞 - B细胞相互作用被激活的问题。结果发现，未致敏的正常B细胞（含有Lyb - 5 +和Lyb - 5 - B细胞），但未致敏的xid缺陷群体（仅Lyb - 5 -）不能被克隆的KLH特异性且MHC限制的Th细胞激活，无论TNP - KLH浓度高低。含有Lyb - 5 +的B细胞对高浓度抗原（10微克/毫升）的IgM反应是MHC非限制的，而未致敏的Lyb - 5 + B细胞对低浓度抗原（0.001微克/毫升）的IgM反应是MHC限制的。因此，未致敏的Lyb - 5 + B细胞可通过MHC限制和非限制途径被激活。进一步证明，即使对于MHC限制的B细胞激活，Lyb - 5 +和Lyb - 5 - B细胞的激活要求也有所不同。
